LCQ18 : Upgrading works for slopes
Following is a question by the Hon Frederick Fung and a written reply by the Secretary for the Environment, Transport and Works, Dr Sarah Liao, at the Legislative Council meeting today (June 7) :
It has been reported that the Government has compiled a list on which upgrading works for various slopes in the territory are prioritized according to their levels of risk. In this connection, will the Government inform this Council:
(a) of the number of slopes where landslides occurred as a result of no upgrading works being carried out in the past three years, whether they have been upgraded and, among them, the number of slopes which had not been included in the above list before the landslides occurred;
(b) whether the authorities have assessed if the occurrence of landslides on the slopes mentioned in (a) reflects inadequacies in the existing system of slope risk assessment; if they have, of the assessment results; whether it will review the system and the upgrading works priority list, and enhance investigations of slopes in the territory;
(c) of the respective numbers of government-managed and privately owned slopes where landslides occurred in the past three years and, among them, the number of slopes which have been upgraded; whether the authorities have looked into why landslides still occurred on those upgraded slopes, and whether they will review the current design of the upgrading works, the existing slope safety factor and drainage requirements, etc, and make improvements accordingly; and
(d) of the number of slopes which are on the above list and were upgraded in the past year; its percentage in the total number of slopes on the list, the number of slopes which are on the list and have not yet been upgraded, as well as the timetable for completing upgrading works for these slopes?
(a) & (b) There are currently some 57,000 man-made slopes registered in the "Catalogue of Slopes" (the Catalogue) in the territory, among which 39,000 are Government slopes and the rest privately owned.
Landslip incidents occurred in the past three years are set out in Annex 1. Among the various landslips occurred in 2003, 04 and 05, there were 93, 94 and 260 landslips respectively involving man-made slopes which had neither been studied nor upgraded prior to the incidents. However, these slopes were mostly located in remote areas where no large-scale development or important facilities would be affected in case of landslips; and hence their potential risk was relatively lower. As such, the slopes concerned had not been included in the Government's annual "Landslip Preventive Measures (LPM) Programme". In fact, most of these landslide incidents were minor ones with no casualty or loss of property. After the incidents, all necessary emergency slope repair works had been completed.
In screening slopes for inclusion in the LPM Programme, the Government would select man-made slopes formed before the establishment of Geotechnical Engineering Office (GEO) in 1977 for assessing the landslip risk according to a“risk-based ranking system”and for determining the priority of studies and upgrading works. Launched in 1979 and fine-tuned in 1995, this system has been operating effectively in assessing the relative probability of impact on life and property caused by slope failures. As for man-made slopes formed after 1977, the compliance with the Government promulgated safety standards and audit requirements would be essential in the design and construction stages.
Apart from the above "LPM Programme", the Government also conducts regular inspections on all Government slopes and completes routine maintenance works before the onset of the rainy season so as to minimise the risk posed to the public by landslips. As for private slopes, the Government carries out safety screening studies on certain high consequence private man-made slopes and issues "Dangerous Hillside Orders" when necessary. The GEO, in a continued effort to educate the public about slope maintenance, also steps up publicity before the onset of the rainy season.
(c) A breakdown of landslip incidents involving upgraded slopes in the past three years is at Annex 2. It can be seen that most landslips were minor ones, while the other four landslips involving a larger volume of debris did not cause serious consequences but only affected open spaces or non-major roads for a short time.
Investigation works are normally carried out after the major landslip incidents involving those Government slopes listed in Annex 2. As for private slopes, the Buildings Department will serve Dangerous Hillside Orders on the owners concerned, requesting them to commission geotechnical engineers to carry out investigations on the slopes and submit proposals for upgrading works. The GEO will draw lessons from these studies and identify areas for improvement. After the investigation reports are completed, the GEO will publish guidelines for improving work practices for reference by Government departments and the industry.
(d) Under the "10-year Extended LPM Programme" from 2000 to 2010, the Government is targeted to upgrade 250 high priority Government man-made slopes and to carry out safety-screening studies on 300 high priority private man-made slopes annually. In 2005, this target was fully met. By 2005, upgrading works were completed for 1,510 Government man-made slopes (over 60% of the target) and safety-screening studies were carried out on 2,210 private slopes (over 73% of the target); well above the target set under the Programme. Works on the remaining high priority man-made slopes under the "10-year Extended LPM Programme" will be completed by March 2010, in order of priority.
End/Wednesday, June 7, 2006